1. Field of the Invention
The invention relates to a method for axial alignment of an assembly for implanting a parietal probe in a reducing-smelting furnace, such as a blast furnace. The invention further relates to the means used to obtain such alignment.
2. Description of the Related Art
Several methods are already known for probing reducing-smelting furnaces, among which probings by substantially vertical introduction of the probe through the top aperture of the furnace, and probings by substantially horizontal introduction of the probe through a hole provided in the furnace wall.
The choice of method is essentially guided by the object of the probing. For example, with blast furnaces, if the probing is more particularly directed to the conditions of temperature or pressure at the top part of the stack, the probe is advantageously introduced through the top, where access through the throat of the blast furnace is easier. On the contrary, to probe the characteristics in the hearth or the boshes, a parietal introduction of the probe is preferred.
In the case of a parietal introduction, the probe, which is composed of an elongated rectilinear body, is pushed inside the furnace through an orifice provided in the outer wall of the furnace and in the refractory lining. In order to keep heat losses to a minimum and to prevent deterioration of the wall near the orifice, the latter is preferably of small diameter. In the particular case of a blast furnace, the passage for the probe is advantageously defined by the orifice of the air blast tuyeres and the diameter of the probe is only slightly smaller than that of said orifice.
Also, due to the high temperatures inside the furnace, and to the noxious gases under pressure therein, the orifice must be made tight, both when the probe is introduced and when it is withdrawn. Tightness is provided by conventional means, generally equipped with a valve or other sealing member, which is closed out of probing periods, and which is associated with a stuffing-box of which the packing encircles the probe when the latter is inserted axially through the tightness device, the valve being then open.
The tightness device can have additional accessories. For example, it can be connected to the wall around the orifice, via an expansion joint which absorbs the deformation differences between the elements subjected to the high temperatures of the furnace, while preserving tightness between the wall and the valve or the stuffing-box.
Due to the thickness of the wall and to the length of the tightness device, the probe must be guided as accurately as possible in order to penetrate without difficulty in the orifice. To this effect, the probe is held, first at the level of the stuffing-box, where it is guided by said stuffing-box or by any adequate device, and second, by an introduction frame which supports the part of the probe not yet introduced into the furnace, said frame being adjustable in height and inclination according to the vertical and to all other directions.
Said frame is used both as a support and guide for the probe, and as a thrusting means, for pushing the probe into the furnace. The thrust is transmitted to the probe by a carriage guided according to a translational movement over the length of the frame and moved by drive members.
An introduction frame for a parietal probe is described for example in U.S. Pat. No. 4,361,315 and a tightness device is described in the U.S. Pat. No. 4,393,703.
The probes used in blast furnaces are normally tubular-shaped, with a cooled wall, and can contain various sampling and measuring equipment. Their length is dependent on the depth to which they are to be introduced into the furnace, and on the length of the tightness device. For a penetration as far as the axis of a modern blast furnace, the length of the probe can exceed 10 meters. The total length of the implanting assembly is therefore important and can reach to around 20 meters.
Because of these great lengths, of the small diameter of the orifice and of the probe (for example less than 100 mm) and of the exerted thrusting force, the probe has a tendency to bend through buckling. Also, due to the cantilever which may be important between the point of support of the probe body on the frame or on the tightness device and the orifice in the furnace wall, the end of the probe nose may move aside of the orifice axis.
In certain cases, the outer wall of the furnace may move with respect to its refractory lining, which can alter the relative position of the orifice in the refractory lining with respect to the tightness device which is joined to the outer wall.
It will therefore be understood that not only should the probe be firmly held and guided on the frame and on the tightness device, but also the axes of both and of the orifice must be in perfect alignment.